A woman who breast-fed her 5-month-old son on an American Airlines flight last month claims in a letter to the company that a flight attendant displayed "inappropriate, harassment-style behavior" when the passenger declined to cover her child with a blanket.

Hannah Butta, who identified herself as a "dear friend" of the mom on the flight, posted the letter on Facebook. The mom herself, according to Butta, asked to remain anonymous.

The airline responded to the woman's complaint in a letter dated July 30 and signed by Tim Rhodes of customer relations. American Airlines confirmed to ABC News that it sent the letter, which has been shared more than 7,500 times on Facebook.

In it, the airline said that breast-feeding is allowed in flight, but "because of the offense that may be taken by others within the close confines of commercial aircraft, we simply ask that breast-feeding be done with a certain discretion and a sense of modesty. We believe it is reasonable that we ask the mother to cover up in an appropriate manner during the feeding and by your account it appears that you were sensitive to this need."

In the mother's original complaint to the airline, she said she was seated in the window seat, her husband in the middle seat and an unrelated girl, whom she estimated to be 10 to 12, was in the aisle.

She wrote in the complaint that a flight attendant walked by while her son was nursing and gave her "a displeased look." Several minutes later, the same flight attendant returned and told her to put a blanket over her son because "there are kids on this flight," she said. Her husband refused.

"A few minutes later, she returned again and told the young lady in the aisle seat, 'I'm going to move you back here because you're probably really uncomfortable,'" the letter said. "By that time, our my [sic] son was asleep and the girl had yet to take notice in my nursing of him."

The woman said the flight attendant did not offer drinks and "avoided looking at us" for the rest of the flight.

In a statement to ABC News, American Airlines spokeswoman Andrea Huguely said, "To clear up a misunderstanding, American Airlines has always allowed mothers to breast-feed during flight. The approach our flight attendants take is to ensure breast-feeding mothers have the privacy they wish to have, while also ensuring the comfort of our other passengers.

"We apologize to the breast-feeding mother who was offered a blanket during a recent flight by a well-intentioned flight attendant. The intent was to make everyone onboard comfortable, including the unrelated 12-year-old sitting in the same row."

The airline acknowledged that what transpired between the mom and the flight attendant should have been "more consistent" with what's in the flight attendant manual. The manual reads, "If a customer's activity causes discomfort to another customer, F/As should use their best judgment to decide whether the activity is inappropriate. A F/A may be called upon to relocate an offended customer to another seat or discretely inform a customer of airline policy. In instances involving customer discomfort, F/As should
use the following guidelines to determine the best course of action."

On the subject of breast-feeding specifically, the manual states: "Breast-feeding of infants is permitted during all phases of flight, F/As should not place restrictions or requirements on the mother of the infant."